1. Field of the Invention
The present invention relates, in general, to a coupling device for explosives, and more particularly, to a coupling device which is configured such that respective explosives for blasting work are coupled to front and rear sections thereof.
2. Description of the Related Art
In a variety of civil engineering and construction work including tunneling work, blasting is performed by forming blasting holes in the ground using a rock drill or the like and then inserting explosives into the blasting holes.
The explosives used in this case are coupled together in line via a coupling device, such as a coupling socket.
Referring to FIG. 1 and FIG. 2, a coupling device 10 for explosives of the related art is provided such that respective explosives 1 for blasting work are coupled to the front and rear sections thereof, and has a plurality of support pieces 11 formed on one portion thereof.
According to the design of the coupling device 10 for explosives of the related art, it is intended to insert the explosives 1 into a blasting hole in the state in which the support pieces 11 are pushed back. However, since it is difficult to insert the explosives into the blasting hole due to friction with the inner surface of the hole, at sites, the designed insertion directions are not followed. Rather, the explosives 1 are inserted in the opposite direction because it is easy.
According to the coupling device 10 for explosives of the related art, there is a problem in that the explosives 1 are not located in the center of the blasting hole and the support pieces 11 are too freely movable. Thus, the explosives 1 may be installed in the state in which they are inclined in one direction, thereby degrading the efficiency of the blasting, which is problematic.
In addition, since it is not easy to insert the explosives 1 into the coupling device 10 because of compressed air, the explosives 1 may be easily detached from the coupling device 10. When the explosives are blown up, the tendency of chain explosion (tendency of sympathetic explosion) is degraded. In addition, there is a possibility that the explosives might fail to explode (misfire).
FIG. 3 is a view showing a method of inserting explosives into a blasting hole of the related art.
Referring to FIG. 3, in the related art, the direction in which the explosives is inserted into a blasting hole may be divided into a forward direction and a backward direction depending on the position of the coupling device. However, the directivity of the forward direction or the backward direction is not essential. The forward direction indicates that the coupling device is positioned on the rear end when the explosives are inserted, whereas the backward direction indicates that the coupling device is positioned on the front end when the explosives are inserted.
First, the forward insertion is a method that is generally used at sites. The explosives can be inserted with no difficulties. If impurities are found in the blasting hole during the insertion, there are no significant difficulties in taking the explosives out in order to inserting them again after removing the impurities.
However, in the forward insertion, accurate centering is difficult because the support pieces of the fastening device are folded. In the case of hardening work, the support pieces are folded and thus do not properly play their role, which is problematic.
Next, the backward insertion is a method in which insertion is performed in such a manner that satisfies the purpose of the manufacture of the coupling device. However, since the coupling device is positioned on the front end, it is difficult to insert the explosives into the blasting hole because of the friction between the wall surface of the blasting hole and the support pieces. After the completion of the insertion, the degree to which the support pieces are bent inside the blasting hole is not as severe as in the forward insertion. However, when the hardening work is performed, as in the forward insertion, it is impossible to prevent the support pieces from being bent.
Furthermore, as shown in FIGS. 4A to 4C, when it is difficult to insert the explosives further due to impurities, such as rock or a tree root, in the blasting hole, it is required to take the coupling device from the blasting hole and insert it again after removing the impurities. However, in the backward insertion, when the coupling device is to be taken out, the support pieces 11 are blocked by the wall surface of the blasting hole. It is therefore substantially impossible to take out the coupling device. When the coupling device is forcibly taken out, the support pieces may be damaged or the explosives may be disconnected from each other (see FIGS. 4A and 4B). In FIG. 4A, reference numeral 1a indicates a primary explosive, and reference numeral 1b indicates explosives.
When the insertion is difficult due to the impurities or the like, at sites, as shown in FIG. 4C, the operation of inserting the coupling device is stopped, and the remaining explosive, which has not yet been inserted, is forcibly bent and is pushed into the blasting hole (indicated by reference sign ‘A’). In this case, however, sealing work (the operation of closing the blasting hole with soil or sand after the completion of the insertion of the explosives) cannot be properly performed since the space is not sufficient for sealing. In addition, inside the blasting hole, the bottom-hole may not be charged (indicated by reference sign ‘B’), such that a blown-out shot (the power of explosion leaks directly through the hole) might occur, thereby failing the blasting work.